77 lines
2.1 KiB
JavaScript
77 lines
2.1 KiB
JavaScript
// Track visible elemnts on the screen.
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const Eyeline = function Eyeline(selector) {
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this.selector = selector;
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};
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Eyeline.prototype.update = function() {
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if (Ember.testing) {
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return;
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}
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const docViewTop = $(window).scrollTop(),
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windowHeight = $(window).height(),
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docViewBottom = docViewTop + windowHeight,
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$elements = $(this.selector),
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bottomOffset = $elements.last().offset(),
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self = this;
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let atBottom = false;
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if (bottomOffset) {
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atBottom =
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bottomOffset.top <= docViewBottom && bottomOffset.top >= docViewTop;
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}
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return $elements.each(function(i, elem) {
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const $elem = $(elem),
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elemTop = $elem.offset().top,
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elemBottom = elemTop + $elem.height();
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let markSeen = false;
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// Make sure the element is visible
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if (!$elem.is(":visible")) return true;
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// It's seen if...
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// ...the element is vertically within the top and botom
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if (elemTop <= docViewBottom && elemTop >= docViewTop) markSeen = true;
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// ...the element top is above the top and the bottom is below the bottom (large elements)
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if (elemTop <= docViewTop && elemBottom >= docViewBottom) markSeen = true;
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// ...we're at the bottom and the bottom of the element is visible (large bottom elements)
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if (atBottom && elemBottom >= docViewTop) markSeen = true;
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if (!markSeen) return true;
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// If you hit the bottom we mark all the elements as seen. Otherwise, just the first one
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if (!atBottom) {
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self.trigger("saw", { detail: $elem });
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if (i === 0) {
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self.trigger("sawTop", { detail: $elem });
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}
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return false;
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}
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if (i === 0) {
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self.trigger("sawTop", { detail: $elem });
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}
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if (i === $elements.length - 1) {
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return self.trigger("sawBottom", { detail: $elem });
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}
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});
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};
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// Call this when we know aren't loading any more elements. Mark the rest as seen
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Eyeline.prototype.flushRest = function() {
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if (Ember.testing) {
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return;
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}
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const self = this;
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$(this.selector).each(function(i, elem) {
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return self.trigger("saw", { detail: $(elem) });
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});
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};
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RSVP.EventTarget.mixin(Eyeline.prototype);
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export default Eyeline;
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